The proportion of UK households where no adult aged 16 to 64 is in work is at its lowest since comparable records began in 1996, according to the Office for National Statistics.

The statistics authority said there were 3.5 million such households in the UK between April and June this year, about 17.1% of all households.

In the same period a year before the figure was 17.9%, and it has been in long-term decline. It stood at 19.2% in April to June 2010.

Some of the change is demographic rather than attributable to a government policy. The ONS said the fall of 182,000 in the number of workless households in the UK was partly due to some households moving from containing at least one person aged 16-64 to containing all people aged 65 and over "and therefore not being included in the analysis".

The ageing workforce had a significant knock-on effect. The ONS stated that there had been a drop of 124,000 in the number of 50- to 64-year-olds who were living in workless households.

This meant that the total number of working age people living in workless households fell below 5 million for the first time since April to June 2008. In the quarter ending June 2013, the number of people in workless households who are aged between 16 and 64 fell by 132,000 to 4.9 million.

By contrast there was a 15,000 increase in the number of 16- to 24-year-olds who were living in workless households.

The ONS said the most common reason people aged 16 to 64 in workless households gave for not being in work was being sick or disabled, with 28% saying this was the reason for not getting a job. This was followed by unemployment (21%), early retirement (17%), looking after the family or home (15%) and study (13%).

Households where no one has ever worked are part of the workless households group and the ONS noted that the number of these households continued to drop since its peak in 2011, when the country had more than 350,000 such households.

In 2013 there were 297,000 households where no one had ever worked, containing 500,000 people. However, analysts have cautioned against overinterpreting this figure: nearly half, or 48%, of these people were students and a further 18% were sick or disabled.

Only 10% – about 50,000 people – had never worked because of unemployment. The remainder either stated they were looking after the family or home (14%) or other reasons (10%).

The data also reveals that single parents are much more likely to be in a workless household than couples with children. The ONS found 36% of households that contained lone parents with dependent children were workless in April to June 2013, which contrasts with 5% of households that contained couples with dependent children.

There were 1.6 million children growing up in households where nobody was in work and most of these children, or 65%, were living in households with just one parent.

Although the number of children living in workless households had risen after the economic downturn, this has fallen to 14% in 2013. This is the lowest since 1996 when the figure was first recorded and revealed one in every five children, or 20%, were living in workless households.